This proposal outlines plans to extend the applicability of the yeast display system, which was developed recently at the University of Illinois for studying protein-protein and protein-ligand interactions. The technology was invented by Dr. K. D. Wittrup, who is listed as a consultant in the present proposal, and by Mr. Eric Boder, a graduate student in Dr. Wittrup's laboratory at the University of Illinois. The yeast display system can display proteins on the extracellular surface of the yeast cell wall, allowing them to interact with the external environment. The yeast display system first was used to isolate antibodies with high affinity for a small molecule. The investigators at Invitrogen Corporation, Dr. K. Madden and colleagues, now propose testing the yeast display system for use in studying interactions between different proteins displayed on two opposing yeast cells. If possible, this system will be used to identify novel protein-protein interactions from libraries of displayed protein, as well as to screen for drugs that can inhibit a given interaction. PROPOSED COMMERCIAL APPLICATION: NOT AVAILABLE